Listen to part of a lecture in a history class.
(female professor) So, most cities of the ancient world tended to be small, often limited to the banks of a river. They had very little means to expand. These old cities couldn't really cross natural barriers like rivers or be located very far from water sources. But Roman cities, on the other hand, grew much larger. How did this happen? Well, for one thing, the Romans had more advanced technology. Let's look at a couple of Roman developments that allowed its cities to expand.One development that'll allow Roman cities to grow was their advanced building materials. The Romans developed a special kind of concrete, a building material that would harden under water. And this concrete made new kinds of structures possible. Take their bridges for example. Because of this special concrete, they could build better bridges, bridges that could go across wide rivers, bridges that were big enough to transport equipment and materials with wagons and carts. So with these strong bridges, Roman cities could grow on both sides of the river, creating larger cities than would have been possible otherwise. Another development that helped Roman cities expand was an improved way to move fresh clean water. People need access to fresh water and the Romans created an especially effective way to bring it to them. They built structures called aqueducts. Now, aqueducts are series of open channels, waterways that stretch from water sources high in the mountains to cities. They were carefully planned and built so the steady drop in altitude provides the steady flow of water to cities. These aqueducts could move tremendous amount of water over great distances and even bring fresh water to places far from rivers. Because of this, people could have clean water for drinking and bathing without being located near a river. So cities were able to grow larger in new locations."
Using the examples from the lecture, explain two developments that allowed ancient Roman cities to expand.
"The first development is the use of new building materials, a special kind of concrete that hardens under water. And this technology allows ancient Romans to build large strong bridges over wide rivers so that cars and wagons can transport equipment and materials on it to create larger cities on both sides of the rivers. Another technology is an improved way to move fresh water, a structure called aqueducts. They're series of open channels that stretch from water sources high in the mountain down to the cities and provide steady flow of fresh water along with the steady drop of altitude. Since the aqueducts can provide plenty of fresh water, they can supply places, even those far away from the river with the fresh water. So cities could grow without having to be built nearby a river. (136 words)"
